Vehicle tire



July l, 1930. R. E. JENKINSON VEHICLE TIRE Filed NOV. lO, 1928 fluor ne11 all Patented lhilly l, i3@

naar

ROSS E. JENKINSGN, 0F

502 @m0, ASSIGNOR T@ THE GGODYEAR TIRE & RUBBER VEHECLE TERE.application le November lo, i928. Serial No. Slfl.

'ifhis invention relates to vehicle tires and it has particular relationto a novel tread element that may be advantageously employed Jtorvehicle tires.

lhe primary object of this invention .is to provide a tread element tortires which is composed or a plurality or? layers, the inner one orwhich is composed oi a ruhbervcomf pound capable of readily transmittingheat generated in the carcass therefrom.

L `further object of the invention is to provide a tread of the abovedesignated character wherein the inner layer is comparatively softresilient, in order to minimize the internai heat generated by poundinget the tread buttons upon the carcass.

.another object ci the invention is to provide a tire embodying a treadelement composed oi" a plurality o layers ot rubber compound whichdecrease progressively in resiliency, soness and the ability to transmitheat from the innermost layer to the outerst layer. s heretoiforeconstructed, pneumatic tires l comprised a carcass consisting of a pluyof inner plies of corel fabric, a breaker ,i disposed upon the cordfabric plies and ced-decl in a relatively thin layer of soit ci shionrubber, and outer tread element relatively hard, stili',abrasion-resistant compound. ln the tires or conventional design, thecushion about breaker strip was composed ore stock containingrapproximately 2f@ parts by weight or" Zinc oxide l0@ parte weight oiZrubber. This material was en tremely soit and elastic, therebypermitting some degree oi movement ore the tread element without un dulystrain ine; the fabric carcass. lUnfortunately this soit compoundoiiered but little resistance to abrasion, after the tread ply had wornaway, and because o Vits low pigment content, it was a poor conductor orheat. Therefore, it was desirable to make it as thin as practicable.,"ln actual practice the thickness of cushion rubber between the breakerstrip and the tread element did not constitute much more than a tenthpart of the entire thickness of tread. rlihis thin layer was not sucientadequately to cushion and to distribute the thrust oi the tread buttonsover the surface oi: the `iabric.

rlihe outer ply of rubber known as the tread element was usuallyprepared from stock containing approximately orty to itity parts byweight of gas black and one hundred parts of rubber. This material oeredhigh resistance to abrasion, but it was relatively stiii1 and inelastic.Therefore, its cushioning action was relatively slight. Furthermore, dueto its stiffness and lack of resiliency and thickness, upon repeatedexure rnuch heat was generated therein. Since the compound was also apoor conductor, the heat generated tended to escape inwardly through thethin laer of cushion rubber and fabric. As considerable heat waslikewise generated in the latter, the temperature or the tire becameexcessive, sometimes reaching values oit 300 in the region of the outerplies o' fabric, thus resulting in carcass failures, such as blowouts.ln tires designed iior operation at high speed, it was necessary toreduce the thickness of the tread ply, thus sacriiicing some of theabrasion resisting rqualities in order to obtain adequate heat radiationto prevent blowout". rThis was particularly true oi large sizes oftires, such as those used on trucks and busses.

This invention consists in the discovery that by orming the treadelements oi2 pneun matic tires or resilient inner ply ci? stock highlyloaded with zinc oxide and an outer ply composed ot stock highly loadedwith carbon black, much less heat is generated and about the fabric, andthe heat that is generated is conducted outwardly more rapidly than intires ot ordinary ccrstructioniz Also, the impacts of the road upon thetread buttons are more uniformly distributed upon the fabric., At thesame time, the resistance to abrasion, characteristic of the old styleof tire-treads is in a great measure retained.

For a better understanding of the invention, reference may now be had tothe accompanying drawing forming a part of the disclosure, wherein isshown a view of a portion of a tire, transversely severed to illustratein cross-section the several elements of the tire, embod ing thefeatures of the invention.

In the embodiment of the invention illus trated in the accompanyingdrawing, a tire carcass 10 is composed of superimposed fabric or cordplies 11, beads 12, and a conventional breaker strip 13. The latter isembedded in a cushion of relatively soft rubber 14, and has mountedthereon a tread element 15, cornposed of an outer layer 16 and an innerlayer 17. The layers 16 and 17 are preferably extruded and haveirregular contiguous surfaces, as indicated at 18, along which they areunited prior to the mounting of the tread upon the carcass.

It is necessary that the outer portion of the tread 15 be of relativelyhard rubber in order properly to withstand the wearing effect of itsengagement with the road. The layer 16 is preferably, but notnecessarily, composed of the usual carbon black compound.

The inner layer 17, which is vulcanized to the carcass 10, however, mustbe composed of a compound having several characteristics necessary tothe proper functioning of the tire in accordance with this invention. Itmust be relatively soft and resilient, in order to cushion the inwardmovement of the layer 16 and particularly of the tread buttons 19, toprevent what is known as tread or button -pounding common in tiresutilized prior to this invention.

The pounding of the tread; that is, the action of the tread upon thecarcass, causes the generation of considerable heat which is the directcause, in some instances, of tire failure by blowout. It is apparentthat the provision of this relatively soft and resilient area betweenthe hard tread 16 and the carcass 10 will do much to obviate thisdifficulty. Also, the layer 17 must be capable of quickly transmittingheat generated in the carcass away therefrom, in order to preventfailure of the plies due to excessive heat.

Any compound which has the general characteristics set forth above maybe utilized and satisfactory results have been obtained by the use of arubber compound commonly known to the trade as zinc stock that is, astock which includes as one of its elements a. large quantity of zincoxide which renders the compound highly resilient and also a goodconductor of heat.

The relative proportions of the various in* gredients in the rubbercompounds employed may vary within relatively wide limits. For example,the stock employed for the outer ly 16 of the tread may contain fromthirty-Eve to iiftyparts by weight of carbon black for each one hundredparts of rubber. AThe following is a typical compound which has beenfound to be quite satisfactory for the purpose Parts by weight Rubber100 Zinc oxide 5 Sulfur 3 Pine tar or other softener 5 Accelerator('mercaptobenzothiazole) 1 Carbon black 43 The inner ply 17 preferablyshould contain from one hundred twenty-five to one hundredv fifty partsby weight of zinc oxide for each one hundred parts of rubber. Thefollowing is asatisfactory formula for this material The relativeproportions of the inner and outer plies may vary somewhat, but for bestresults the inner ply should constitute from a fourth to a third of thewhole tread. If approximately these proportions are employed, thecushioning effect of the tread upon the carcass is greatly increased,thereby reducing both iiexure and the amount of heat generated in thelatter. Furthermore, since the layer 17 has higher resiliency thanordinary tread stock, less hysteresis loss occurs therein, andconsequently there is less generation of heat in the reg-ion adjacentthe fabric. Finally, the zinc stock has a higher coefiicient of heatconductivity than common tread stock. Therefore, the heat generated inthe fabric plies is radiated more rapidly than in tires of ordinarydesign.

Any standard cushion stock may be employed for the cushion ply 14.-,butpreferably a compound containing from fifteen to thirty parts by weightof zinc oxide for each one hundred parts of rubber should be selected.This stock should not contain over five percent of carbon black.

The layer 1.7 is preferably utilized only adjacent the outer portion ofthe tire while the layer 16 engages the side-walls of the body l0 in theusual manner.

From the foregoing description it will be apparent that this inventionis applicable to some forms of cushion tires as well as to casings forpneumatic tires, as shown.

Although I have illustrated only one form which the invention may assumeand have described in detail only a single application' thereof, it willbe apparent to those skilled in the art that it is not so limited, butthat varlous minor modifications may be made therein without departingfrom the spirit of the invention or from the scope of the appendedclaims.

What l claim is:

1. A tread element for vehicle tires comprising an outer ply of stockcontaining approximately 43 parts by weight of carbon black for parts ofrubber, and an inner ply containing approximately 140 parts by 1wgeightof zinc oxide for each 100 parts of rub- 2. A tread element for vehicletires com prising an outer plyof stock containing between 35 and 50parts by weight of carbon black for 10() parts of rubber, and an innerply containing between and 150 parts by weight of zinc oxide for each100 parts of rubber, each of said plies having irregular contiguoussurfaces.

3. A pneumatic tire comprising a fabric carcass and a tread elementsecured thereto, comprising an inner ply of stock composed ofapproximately parts by weight of zinc oxide for each 100 parts ofrubber, and an outer ply composed of stock containing approximately 43parts of carbon black for each 100 parts of rubber.

A1. A pneumatic tire comprising a-.fabric carcass and a tread elementsecured thereto, comprising an inner ply composed of stock containingbetween 125 and 150 parts by weight of zinc oxide for each 100 parts ofrubber` and an outer ply composed of stock containing between 35 and 50parts by weight of carbon black for each 100 parts of rubber.

In witness whereof, I have hereunto signed, my name.

Signed at Akron, in the county of Summit and State of Ohio, U. S, A.,this 9th day of November, 1928.

, ROSS E. JENKINSON.

